Interaction between linker and TI loop influences the structural integrity of the active site.

(A–C) Electrostatic potential surfaces of the phosphatase domain calculated with the APBS tool [26] are shown. Representations of (A) the wild type model at 0 and after 50 ns of the MD simulation, (B) the crystallographic structures by Liu et al. of the IP₃ bound conformation (PDB 3V0H) and (C) the PO₄^3–bound state (3V0G) [14]. Negatively and positively charged regions are colored in red and blue, respectively. The yellow element marks the linker residues 252–257. Encircled in yellow is the immediate environment of the catalytic cysteine C363. (D) The aligned backbone structures of the phosphatase domain of the WT (grey) and the corresponding TI loop mutant (yellow) are shown. The P loop containing C363 is highlighted with a dashed circle in red. The linker motif K252-K257 of the mutants is indicated in cyan. Additionally, the figure contains the rmsd values for the structural deviation between wild type and the respective mutant.